CONTENTS. 



OCEAN MAGNETIC OBSERVATIONS, 1905-1916, 

 BY L. A. BAUER, W. J. PETERS, J. A. FLEM- 

 ING, AND J. P. AULT. 



Introduction by L. A. Bauer. 



Previous ocean magnetic surveys 3 



The Magnetic Work of the Galilee, 1905-1908, by 

 L. A. Bauer, W. J. Peters, and J. A. Fleming. 



General remarlis 5 



Description of the Galilee 6 



Charter-party of the Galilee 8 



Synopses of the Galilee's cruises, 1905-1908 10 



Cruise I, August to December 1905 10 



Cruise II, March to October 1906 11 



Cruise III, December 1906 to May 1908 12 



Methods of work on the Galilee 14 



General principles followed 14 



Regarding observation forms 16 



Magnetic instruments used in the Galilee work ... 17 



General considerations 17 



Sea instruments for magnetic declination 17 



Sea instrument for incUnation and total intensity. 1 9 



Description of sea dip-circle used on Cruise 1 . 20 

 Improved sea dip-circle used on Cruises II and 



III 21 



Sea instrument for horizontal intensity 23 



Description of sea deflector 24 



Mounting of magnetic instruments on the Galilee. 26 



Cruise I, August to December 1905 26 



Cruises II and III, 1906 to 1908 27 



Land magnetic instruments 28 



Instrumental outfit for the Galilee work 28 



Cruise I, August to December 1905 28 



Cruise II, February to October 1906 29 



Cruise III, December 1906 to May 1908 31 



General property and supplies 33 



Specimens of observations and of computations . , . 33 



Magnetic observations during swing of vessel ... 33 

 Declination observations, San Francisco Bay, 



May 25, 1908 33 



Horizontal-intensity observations, San Fran- 

 cisco Bay, May 25, 1908 36 



Total-intensity observations, San Francisco 



Bay, May 25, 1908 39 



Inclination observations, San Francisco Bay, 



May 28, 1908 43 



Summary of results of swings, San Francisco 



Bay, May 23, 25, and 28, 1908 45 



Magnetic observations made on course 40 



Declination obseri'ations, April 14, 1908 47 



Horizontal-intensity observations, April 14, 



1908 49 



Total-intensity observations, April 14, 1908 . 50 



Inclination observations, April 14, 1908 53 



Computation of magnetic observations, April 



14, 1908 55 



Summary of results of observations made on 



course, April 14, 1908 57 



Shore magnetic work 58 



Determination of geographic position at sea .... 58 



General methods 58 



Accuracy of positions at sea 59 



Reduction formulae and determination of constants. 60 



Constants and corrections for sea instruments . . 60 



Declination observations 60 



Horizontal-intensity observations 63 



Inclination observations 64 1 



Total-intensity observations 65 ! 



page 

 OCEAN MAGNETIC OBSERVATIONS— Con. 



Sea dip-circle corrections 66 



Discussion of sea dip-circle corrections 70 



Constants and corrections for land instruments . 75 



Descriptions of magnetometers and dip circles . 75 



Magnetometer corrections yg 



Land dip-circle corrections jg 



Magnetic standards adopted 77 



Ship constants and deviation-coefficients 78 



Fundamental equations 78 



Deviation formulae 73 



Deviation coefficients for Cruises I, II, and III . . 80 



Cruise I, August to December 1905 81 



Cruise II, February to October 1906 82 



Cruise III, December 1906 to May 1908 84 



Adjustment of deviation-coefficients and deri- 

 vation of parameters 86 



General remarks 89 



Starboard angle at the three positions of the 



Galilee instruments 89 



Deviation-constants for chief vessels engaged 



in ocean magnetic work 91 



Specimen computations of deviation-correc- 

 tions 91 



Ocean magnetic observations on the Galilee, 1905- 



1908 93 



Explanatory remarks 93 



Combining weights assigned to different in- 

 struments and methods 95 



Distribution of stations gg 



Observers and computers gg 



Final results of ocean magnetic observations on the 



Galilee, ig05-1908 97 



Cruise I, Pacific Ocean, 1905 97 



Cruise II, Pacific Ocean, 1906 99 



Cruise III, Pacific Ocean, 1906-1908 101 



Shore magnetic observations for the Galilee work, 



1905-1908 105 



Explanatory remarks 105 



Results of shore magnetic observations, 1905- 



1908 105 



Descriptions of shore stations, 1905-1908 110 



Extracts from Director's instmctions for cruises 



and observational work on the Galilee 115 



Cruise I of the Galilee, 1905 115 



Cruise II of the Galilee, 1906 118 



Cruise III of the Galilee, 1906-1908 125 



Extracts from field reports and abstracts of logs of 



the Galilee 128 



Extracts from field reports 128 



J. F. Pratt: Alterations of the Galilee, and her 



first cruise 128 



W. J. Peters: Discussion of alidade correction 



for standard compass R3C 134 



Abstracts of logs of the Galilee 141 



J. F. Pratt: Abstract of log. Cruise I, 1905. . . 141 

 Summary of passages for Cruise I of the 



Galilee 143 



W. J. Peters: Abstract of log, Cruise II. 1906 . 143 

 Summary of passages for Cruise II of the 



Galilee 146 



W. J. Peters: Abstract of log, Cruise III, 1906- 



1908 147 



Summary of passages for Cruise III of the 



Galilee 154 



Summary of passages for all cruises of the 



Galilee, 1905-1908 154 



Auxiliary observations on the Galilee 154 



